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An understanding of long-term tillage and straw management impact on soil structure and productivity is necessary for the further development of conservation tillage practice in dryland farming areas. Data from a 15-year field experiment conducted in Shanxi, on the loess plateau of northern China, were used to compare the long-term effects of no-till and residue cover (NTSC) with conventional tillage (CT) in a winter wheat (Triticum aestivum L.) monoculture. Long-term CT and straw removal resulted in poor soil structure and low productivity. Mean soil bulk density in NTSC was 1.5% less than in CT and capillary porosity (<60 μm) 3.2% greater. Water stability of macro-aggregates >2 mm was much greater for NTSC in the 0–0.20 m profile. Soil organic matter and total N and P were 27.9%, 25.6%, and 4.4% greater in NTSC, respectively, and earthworms (19/m2) were found only in the no tillage treatment. Crop yield and water use efficiency tended to be higher under NTSC than under CT, especially in the years of low rainfall, suggesting that the change in soil structure has provided a better environment for crop development. Our 15-year experimental data indicate that NTSC is a more sustainable farming system, which can improve soil structure, and increase productivity with positive environmental impacts in the rainfed dryland farming areas of northern China.

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Soil degradation and subsequent yield decline are the main factors limiting further development of agriculture on the farming-pastoral transition zone of China. A 10-year field experiment was conducted in Inner Mongolia to compare the long-term effects of no-tillage with straw cover (NT), subsoiling with straw cover (ST), rototilling with straw cover (RT) and traditional tillage (TT) using ploughs on soil properties and productivity in a spring wheat-oat cropping system. Long-term conservation tillage increased soil organic matter in the top 20 cm by 21.4%, total N by 31.8% and Olsen's P by 34.5% in the 0-5 cm layer compared to traditional tillage. Mean percentage of macro-aggregates (>0.25 mm, +20%) and macroporosity (>60 lm, +52.1%) also improved significantly in the 0-30 cm soil layer (P < 0.05). The largest yield improvements coupled with greatest water use efficiency (WUE) were achieved by no-tillage with straw cover. Ten-year mean crop yields increased by 14.0% and WUE improved by 13.5% compared to traditional tillage due to greater soil moisture and improved soil physical and chemical status. These improvements in soil properties and productivity are of considerable importance for the seriously degraded soils in semiarid Inner Mongolia, as well as for food security, sustainable agriculture and carbon storage in the farming-pasture transition regions of China.

Water is the most limiting factor for crop production in dryland farming. A better understanding of the long-term impact of tillage and residue management systems on soil structure and water infiltration is necessary for the further development of conservation tillage practice to improve water use efficiency. The objectives of this study were to assess the influence of no-till with residue retention (NT) and conventional (plough) tillage with residue removal (CT) on soil properties and soil water transmission characteristics in a winter wheat (Triticum aestivum) monoculture system in Shanxi, on the Chinese Loess Plateau. Soil physical parameter measurements were made in the top 30 cm depth in September 2007 after 16 years under the two tillage treatments. Compared with CT treatment, NT significantly (P < 0.05) reduced soil bulk density (7.1%) in the 20-30 cm soil layer, and increased macroporosity (>60 µm, 17.0%) and saturated hydraulic conductivity (249%) in the 15-30 cm soil layer. There were no significant differences in these soil physical properties between tillage systems in the 0-15 cm layer. In addition, plant available water and water infiltration rate were greater in the NT treatment. The improved soil quality parameters and water infiltration from this long-term experiment indicate that no-tillage with residue retention is a promising farming system for the dryland farming areas of northern China.

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